The epicyclic reduction gears are frequently used in reduction units of aircraft turboprop engines, to allow a reduction in speed between the drive line and the propeller.
The teeth are major elements of the reduction gear since they transfer the power from the input shaft to the output shaft.
Typically, an epicyclic reduction gear comprises a combination of coaxial elements, one or more of which are ring gears, planet carriers which rotate around the common axis and which carry one or more planets meshing with one or more sun gears.
And in some cases, it is useful that the ring gear or gears be made in two parts which are assembled.
Thus, in an epicyclic or planetary gear train, on a herringbone toothing, namely a toothing composed of two helical gears set in opposition so as to cancel the axial force as it is necessary that one of these elements, the sun gears, the planet gears, or the ring gears, be in two parts.
For manufacturing reasons, it is preferable that the ring gear be in two parts, that is to say in two half-ring gears, with the understanding that the expression “two half-ring gears” means two annular rings, a priori identical, or essentially identical, but each has, coupled with the common axis of the half-ring gears, a lesser thickness (for example by half) with respect to that of the final ring gear obtained by the coaxial assembly of the two half-ring gears.
Given that the aim here is to ensure a zero radial clearance between the two half-ring gears in question, which imposes a interference fit between them, and that it is possible for a tooth of one of the half-ring gears not to be aligned with the corresponding tooth on the second half-ring gear, a problem therefore arises regarding the offset of the teeth of the half-ring gears in relation to each other: how to assemble these half-ring gears assembled while ensuring the alignment of their teeth?